Ctrl + B not working with vertex
Blender makes a distinction between CtrlB, Bevel Edges, and CtrlShiftB, Bevel Vertices.
So, use the other shortcut, or, having reached the Adjust Last Operation panel visible in your illustration, switch at the top from 'Edges' to 'Vertices'.
(In other panels, or the Bevel modifier, it might be a small checkbox - 'Only Vertices')
I didn't realize.. as @moonboots has pointed out - there is a hitch in some Blender 2.90.x's meaning the shortcut doesn't work: you have to go to the panel, and switch it there.